Why opDispatch uses SFINAE implicitly?

[Dukc via Digitalmars-d]

If I define an opDispatch for something, but the call does not 
compile, the compiler currently behaves as if the opDispatch 
didn't exist at all. Just like C++ templates as  far as I know. 
Why is this? I think it would be better if it acted like other D 
templates: Compilation failure is always an error, but you can 
use preconditions if you want the "substitution failure is not an 
error"-idiom. This would be better to detect errors.

Is there any way to define a dispatching type so that it errs or 
at least announces if the call does not compile?